A network can be formed by an access point and multiple stations (or network devices) in communication with the access point. Communications between the access point and the multiple stations can occur during one or more uplink periods and one or more downlink periods. For example, during an uplink period, a station may transmit data to the access point; and during a downlink period, a station may receive data from the access point. An access point may periodically transmit beacons to inform a station of various communication-related information—including, for example, i) when the access point has data for the stations, ii) when data is to be transmitted from the access point to the stations, and/or iii) when the stations may transmit data to the access point.
Each of the beacons may include a traffic information message (TIM) and/or a delivery traffic information message (DTIM). TIMs are transmitted to the stations to indicate when unicast data, broadcast data, and/or multicast data is buffered to be transmitted from the access point to the stations. A DTIM is a special TIM. DTIMs not only indicate whether an access point has data (e.g., buffered unicast data, multicast data, and/or broadcast data) to be transmitted to a station, DTIMs also indicate that buffered multicast data and/or broadcast data is to be transmitted subsequent to beacons that carry the DTIM. The DTIMs may be transmitted less frequently than the TIMs.
Each station in a network or basic service set (BSS) may “wake” from a power save mode prior to a time when a DTIM is expected to be transmitted from and/or received by an access point. This allows the stations to determine whether the access point is to transmit multicast data or broadcast data for the BSS, a multicast group and/or a broadcast group in which the stations are assigned. Each station in a network may not wake for each transmitted TIM. Each station may wake for assigned TIMs and remain in a power save mode for other TIMs. This allows the stations to remain in a power save mode for increased periods of time. A station that operates according to a power-saving scheme is also referred to herein as a “power saving station”.
An access point configured to satisfy traditional Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards may support up to 2007 power saving (PS) stations for a single channel. According to 802.11, a single channel may have a bandwidth of 20 mega-hertz (MHz) or 40 MHz. According to IEEE 802.11ah, a station may have a channel bandwidth of 1 MHz or 2 MHz. IEEE 802.11ah requires that an access point support 6000 or more stations in a single channel. This requirement is introduced for “smart grid” applications. A “smart grid” application refers to an application that includes a network with 6000 or more stations, which are located in residential homes and/or business facilities with associated power meters. Although an increase in the number of stations supported by an access point provides increased network coverage per access point, the increased support can result in increased beacon duration times and/or cause channel congestion and increased channel access delays.